For example, it is known from FR-2 863 109, a device for receiving and/or emitting an electromagnetic wave, comprising a plurality of passive reflective elements. The passive reflective elements are periodically spaced inside the device, and said device uses specific Bragg law electromagnetic properties.
However, the passive reflective elements are spaced from each other of a distance that is a multiple of the wavelength λ. The distance is about λ/2 or greater and such device has a large size.
It is also known from the patent application WO-2008/007024, a device having a reactive type antenna element surrounded by a plurality of metallic diffusers. Thanks to this arrangement, the electromagnetic wave is focused to a point i near the antenna element at a sub wavelength distance. Such device does not near to have a period pattern of metallic diffusers.
However, such device does not have a preferred direction for the electromagnetic wave.
All these devices still need to be improved, in the view of increasing their efficiency and reducing their size.